System of electrical control



C. F. SMITH.

SYSTEM OF ELECTRICAL CONTROL.

APPLICATION HLED MAY 15. 19]].

1,368,462. Patented Feb. 15,1921.

, [NVENTOR ATTDRNEYS UNITED STATES CHARLES E. SMITH, OF OLE ELUM, WASHINGTON.

SYSTEM OF ELECTRICAL CONTROL.

Specification of Letters Patent.

Patented Feb. 15, 1921.

Application filed May 15, 1917. Serial No. 168,765.

y invention relates to improvements in systems of electrical control, especially where such electrical systems are made use of in mining operations, and it consists in the combinations, constructions and arrangements herein described and claimed.

An object of my invention is to provide a device which will automatically connect the main feed wires with the distributing system leading to the mine, whenever power is used in the mine or in connection with mining work, and which will automatically cut ofi the general distributing system from the feed wire when the current is no longer in use, thereby rendering the wires of the distributing system harmless as far as accidents to the workmen or fires caused by short circuits etc., are concerned.

A further object of my invention is to provide a controlling device having an element which may also be used as a detector for grounded circuits, thereby indicating that the line is either in good condition to receive the high voltage, or vice versa.

A further object of my invention is to provide a'controlling device of the type described which has fe w parts, and which, therefore, is not easily liable to get gut of order.

Other objects and advantages will appear in the following specification and thenovel featuresof thedevi'ce will be particularly pointed'out in the a pended claims.-

My invgntion is i nstratedin the accompanyin'g fawingdorm'in part of this application, this drawing eing a diagrammatic view of the various parts of the system of electrical control.

In the present instance I have shown the drawing as illustrating a system in which the return circuit is grounded, as for instance, a trolley system in which the rails form the return conductor, but it will be understood that the same system of control could be applied to those systems having a metallic return without departing from the spirit of the invention.-

Referring to the drawing, 1 denotes the A contact 8 is connectcd with the main wire 9 of the distributing system, in this instance this wire being a trolley wire.

The switch 2 is connected by a conductor 10 with the coil of a magnet 11, the opposite end of the coil being connected by a conductor 12 with a variable resistance 13, the op 'wosite terminal of the variable resistance being connected by means of the wire 13 with the main wire 9 of the distributing system.

Pivoted at 14 is a lever 15 which is arranged to swing from the full line position shown in the figure to the dotted line posi tion, thereby closing the contacts 7 and 8. This lever 15 is normally in engagement with the end of a plunger 16, which forms a core of the solenoid 11. One end of the core 16 is pivotally attached at 17 to a lever 18, which is pivoted at 19. The opposite end oi the solenoid core 16 rests against the lever 15, but is not connected to it. The lever 18 is normally held in the fullline position shown in the drawing by means of a spring 20, which is provided with an adjust-lin device 21, so as to vary the tension of the spring.

From the foregoing description of the system the operation thereof may be readily understood.

Before setting the device in condition for working, the attendant at the central station opens the switch 3 and closes switch 2. If any of the main wires of the system should be grounded the plunger 16 will be raised, thus indicating the condition of the line, because sufiicient current will pass through the magnet 11 to cause it to act. If on the other hand there is no action of the magnet 11, then the attendant knows that the line is in working condition. He now opens up the switch 2 and closes switch 3, after which the switch 2 is again closed. The device is now in condition for service.

As long as there is no need for current, the main distributing wire 9 has a relatively low voltage. In many mines wires are carried along ver narrow passe eways that are wet and whic must be u as traveling ways for employees, as well as for hoisting, pumping, ventilating and hauling purposes. Vhen such wires have large voltages the dan er to the employees is great, so that it is esirable to reduce the voltage on the wires except at the times that the current is actually used. When the working-circuit is closed, as for instance when the switch S, which supplies the motor M with current, is closed, this will cause the solenoid 11 to pull up against the tension of the spring 20, thereby bringing the conducting bar in position to connect the contacts 7 and 8. This will complete a circuit through the solenoid 6, which is made of relatively large wire, thereby permitting an increased voltage to be impressed onithe line 9. The fact that the re sistance of the solenoid 11, together with the variable resistance 13 is relatively great causes the greater part of the current to flow through the bar 15, and not through the solenoid 11. The tension of spring 20 pulls the core of the solenoid away from the bar 15.

Now, when the current is shut ofi' from the tool or other machine or electrical appliance which is being run on the circuit bar 1.J which is being held in position by the magnet 6, will drop downwardly, thereby breaking the circuit at the contacts 7 and 8, leaving the device in position to be started up a ain through the action of the magnet 11. he variable resistance 13 may be adjusted to' overcome the line leakage and with the assistance of the coil spring 20 to prevent action of the magnet 11 due to leakage. The variable resistance 13 must be adjusted so as to allow enough current to pass through the coil 11 to energize it under normal conditions, and to lift the plunger 16 when required. It should be regulated to allow enough voltage to be impressed on the wire 9 so that if one of the employees should come in contact with the wire 9v or with a wire leading from. the wire 9, it would act, as a warning and keep him from coming in contaeti-with itcarelessly, butithe resistance 13 should-be adjusted so as to preventsuch a voltage as would endanger human life:

Normally the switch 25 which i'sin series withra varlable resistance 26 is open, Thus on a line in a mine; there is generally so much dampness that there is constant leakage so that the voltage of the line would be kept down. If, however, there is no line leaka e then the resistance 26 might be brought into use for keepin the voltage below the danger point. Un er these circumstances the switrh 25 would be closed. The resistance 26 as will be seen, is grounded on the rail 27. This resistance 26 is an extra safety precaution which ninety-nine times out of a hundred would not be necessary because of line leakage in most instances, but may be brought into use by the closure of the switch 25 when there is no line leakage.

I claim:

1. In a system of electrical control, a feed wire, a distributing wire, an electrically op erated switch arm in series with said feed wire and said distributing wire, a return circuit normally disconnected from the Said distributing wire, a locking magnet for holding said elfix'il'll; switch arm 1D closed osilion, a pair of contacts arranged to be c osed by said switch arm, one of said contacts having connection with said distributing wire, the other of said contacts having connection with one terminal of the winding of said locking magnet, the opposite end of said locking magnet being connected with said feed wire, and a variable resistance for adjusting the voltage-for operating the electric switch arm.

2. In a system of electrical control, a main feed wire, a main distributing wire, a return normally disconnected from said main distributing wire, a solenoid having a movable core, the winding of the solenoid being in series with the feed Wire and with the distributing wire, a switch arm arranged to be engaged by said solenoid core, a pair of contacts arranged to be closed by said switch arm, one of said contacts being connected with the main distributing wire, a locking magnet adapted to holdthe Switch arm in its shifted osltion, one end of said locking magnet eing connected to the other contact and the opposite end ofthe looking magnet being connectediwith the-feed-wire, spring means for opposing the movement of. the core of the solenoid; and-a variable resistance in series with the windin ofthe solenoid;

cnafitas a. snrrn. 

